Ultra-short wave transmitting and amplifying tube



vsaid electromagnetic wave.

the interaction cycle.

Patented Mar. 31, 1953 ULTRA-SHORT WAVE TRANSMITTING AND AMPLIFYING TUBE Alfred Lerbs, Paris, France, assignor to Compagnie Generale de Telegraphie Sans Fil, a corporation of France Application' February 12, 1949, Serial No. 76,096

7 claims. (c1. 179-1171) E co-pending application, Serial No.y l794,164, rfiled on December 27,1947, now'Patent 2,511,407,

issued June 13, 1950, a tube is described wherein use'wasV made of' an electromagnetic wave `propagated at a'certain speed in a circular'guide, and wherein the use of a radial electric fleldand of a'V transverse magnetic neld has the effect of imparting to theelectrons of a beam a circular movementzparallelfto said guide,` during which movement they are in a state of interaction with This tubefwas constructed in such a manner that said electromagnetic wave had the same speed as the electrons, so as to increase its efficiency and its power. The guide through which said wave is adapted to pass could be'constructed in any form that would produce and determine the progression of said'wave, in particular in the form of an articial line that can be obtained either by suitably dimensioning the resonant cavities of a split anode, or by using a solenoid of circular shape, or in any other suitable'manner.' Means have been provided in the aforesaid patent application, for enabling said tube to be used as a power amplier, said means being in particular intended to prevent the production of oscillations, vand to prevent all the electrons, after they have passed through the state of interaction, during a cycle of rotation, with the field of the electromagnetic wave, from returning to said Iield. For this purpose, in particular,they were collected by means of an additional electrode located between the output and input circuits of the tube.

I have discovered that a fraction'of the electrons thus collected had not been in a state of complete interaction with the wave and that it was advantageous, in order to obtain maximum power'from the tube and make it operate at high eciency while retaining its stability of operation, to make said fraction of electrons repeat I also discovered that the electrons which have completely interacted, when travelling through a space bounded by a pair oi electrodes across which a potential difference has been'applied, travelled through a zone near the electrode which was raised to a higher potential, whereas the other electrons, which have not completely interacted, remained closer to the electrode which was raised to a lower potential.

The present invention has for its object a novel cycle, and on the other hand the other electrons,

yembodiments thereof.- k

which have' incompletely interacted, vvare 'again directed into this electromagnetic eld.

- According to the invention, the space between the electrodes that bound the circulationl space for the beam is divided into two channelsfone being terminated by the means for stopping the electrons of the iirst category, the other allowing the electrons ofthe second categorytopass and directing them towards thev eldof the traveling wave so that they can repeat ythe interaction cycle. Y .y A, l

This latter channel is obtained, in particular,

Aby dividing the electrodes into fractions, orgvby inserting additional electrodes and giving them suitable lvoltages so that when said second category of electrons enter again into the electromagnetic field, they acquire thefmost favorable-phase for their interaction; Said phase-mustonthe other hand be so adiustedthatthe risk of producing oscillation is reduced to a minimumf f;

According to a modficationof the invention, ,the phase of said electrons is also adjusted by acting' on the magnetic field ofthe tube.V The invention will be more clearly understood by means of vthe accompanying. iigures which show, by way of non-limitative examples, several Fig. 1' shows diagrammatically a tube constructed according to the `aforesaid patentapplication. Y -v Fig. 2 shows an embodiment of the invention, whichcomprises means `for collecting the electrons that have completely interacted, while Ythe other yelectrons continue on their course around the circular. path.

Fig.3 shows the location of the device of Fig. 2, in a complete tube, only half ofl which is shown, and which comprises between S and E an #inoperative portion of the tube. By inoperative portion is to be understood the portion whereinv the electrons continue on their course but wherein, since'there is no iield, there is no interaction.

Figs.,4 to 7 show several embodiments of the invention, which enable the phase adjustment of the electrons which areintendedto bereturned to the electromagnetic held, these devices Valways being located in the inoperativeportion. f

Figs; 8 to l1 show a particular embodiment of Vthe tube that enables a'differential acceleration to beimparted to the electronsin the inoperative portion of the'tube; v

In Fig. l, a tube according tothe aforesaid patent application isfshown diagrammatically.- A beam emitted by a cathode Canows `through'the interaction :space-bounded lon .the inside by` a circular electrode B. In order to give a definite idea, the emitting strip C has been directly arranged on B, and the whole electrode is connected to the negative pole of the source Si of the radial electric field, so that hereinafter B will indiscriminately be designated as the cathode. The outenelectrode, which is "connected to the positive lpole 'of lthe source SI of the field 'and is consequently called the anode, is divided into two circular portions H and A, each of which occupies an arcfaof Aless than '360 and which are complementary to one another "to form a complete circle. H denotes the portion of the anode formed by a spirally woundiwire and is of circular shape. E represents 'the input'circuit to which is fed the ultra-short-wave to be ampled and S representsthe output circuit from which the amplied power is obtained. The parameters of the tube .are so chosen *that Tsaid Wave sets up, in the space between the anode and 'thefcathode-an electromagnetic-.held which gradually moves forwardsfat the isame speed l'asthe electrons ``eri1`itted by the stripC Ylocated tnear the linpiitlcircuit. `The cathode -Bneed 'not ibecompletely covered` with a'nemitting substance Lprovided'that "the strip rC ispreferably located nea-retire input eirc'uitfE. l A denotes'the fraction of the'.arioiethat'does-not participate inthepropagation of tlief'electromagnetic wave and`I denotes fthe-:lectrode which iis "connected to fthe positive terminal of a source of potential S2 electrons =afterthey lliave'fe'ii'ected'afc'orriplete "cycle of -ro- 'tatihshownfby tli'e arrows vbetween the circuits E fand S. V'I'h'e magnetcexcitation field of the 'tube isffepresented'bythecross M 'and' is Tat right "ahg'lsV to the' planev of vvthe drawing. "The electric v"fieldis radial and iis@ directed from the cathode towards "the anode4 which is Vgiven apositive potential relatively fto the cathode.

I havedisc'ove'red that'such-'a tube, although A 'ardthaving 'the draw'back of lproducing oscillatioris, andhaving theadvanta'ge `of stableoperation, is of veryflow'eiliciency "sinceall theelect1-ons are: iniiscrim'inatelycollectedj by 'saidA elecftrode {"fand consequently '-L'iroducehig'h 'power l'losses In order to increase thee'iciency, according tofthe' V`invention,foly thoselectrons' which' have "completely interacted are-fstopped-an'd the other electrons are allowed to effect a fresh interaction =`cycle.

*An embodiment o'f the tube that *enables this "result 'to bef obtained' is shown in"`Fig. l 2 wherein the :same reference rsymbols denote the same members as in Fig. 1. This figureon'ly 'shows a -ration of "1, Atain-5min the anode 'space A =between the f input Tand output fc'ircuits, wherein 'f A"cours'e"1tlie electrode I has been eliminated. fr"Be'tweerrthe vanode '5A --and Vthe "cathode "B are arranged VAtwo "electrodes '-'Arand A2 which 4are 'connected to a' positive potential relatively to the cathode -'(Which, in the present example, is 'at Vzerov potential), said "potential Vbeing adjustable lwi'thf'respect to the potential* of the anode A,'this lliaving'lbe'en"denotedby the symbol Uar l- Ua. vBy jadjusting :this Ipotential, it is possible to vary the speed 'ofthe electronsfand-therebyadjust the ll'numberof iele'ctr'onscollected. The electrons "which fha'v'e interacted lwith the waveV and which, ".ingeheral, are .located in 'regions near the anode, are collected by this additional electrode A1, "Whereas the'felectrodeP-'Aawhich is located along fan fequipotential lineflthereby inet altering lthe `fdi'stl'fibution oftthe' flldaandrnot disturbing the snow ofithe eleetmnsforrnswithfthe cathode IB,

a duct through which the electrons which have not participated at all in the interaction or which have only incompletely participated therein, are

again directed towards the electromagnetic field. 5 'I'he distances between said electrode A2 and the anode depend on the parameters of the tube, 'zthe 'anode voltage and 'the Lmagnetic'ffield.

In Fig. `3, wherein the same members are denoted by the same reference symbols as in Fig.1, the location of said additional electrodes A1 and .Aahasbeen shownrelatively to the anode portio'n JE`S through Vwhich the electromagnetic wave passes.

The electrons :which have not been collected "penetrate'fagainiinto the input circuit and repeat their'interaction with the electromagnetic wave. Inaorderrto-increaseithe eiiicienoy of the tube and at the same time prevent any self-oscillation, it is limportant to give said electrons, at the instant when they reach the terminal E, a suitable phase with :respect E to `the .phase Tof L4.theV electromagnetic wave. Such phase depends on .theftransit time 4fof 'the electrons between the terminalsS and VnE -(see Fig. 3). Said time is -defined'by therspeed of the electrons and the length of thepath'S-E. For a'given length, the phasel may be'adjusted :byacting on the speed. This-can 'beeiectedin particular :by f changing 'fthe intensity 'of the -'Selectric fieldover this electron pathbroverzapart of "said path, Aor thezintensity :of the magnetic eld the Y* speed Vof the 'electrons .being given 'by `the Uequation .in which Cisa constant'and ,E 'and-B theintensities of the electric Zand :magnetic ifields. Several r embodiments of @this adjustment are :described hereinafter.

-According to Fig. '4, thefanod'e A isdividedinto .fractions-andv provision isimadeitherein .of :a segment A3, the lpotential of which is adjusted in a suitable` manner. Fig. 3,:the-position of fthisdevice has been -shownwith respect tothe nother electrodes of the tube, -in :particular the collecting electrodes LA1, A2.

According 4to 'another embodiment :shown 1 4in Fig. 5, the'phase of theV electrons is adjusted by providinga Ygap 'in the electrode 'A and placing .oppositesaid gap Tan additional` electrode A4,` the potential of which is adjusted in a'suitable'm'an- Iner. This embodiment vhas lthe 'advantage "of preventing the regulatingielectrode v'from collecting, in certaincases, al portion of thepelectrons.

`According to Fig.l 6,-thessame'resultis 'obtained rby .dividing the cathode B :into"fractl'ons andjpro- -viding -thereinfa vsegmentxBi 'ofva cylinder, the voltage ofwhich' isadjusted so as'toeiectthede- `siredfdistribution'oi? the velectric eld.

:According-ton Fig. '7, which is equivalent xtoEig. 25, a -segment FB2, the 4potential of which :is -Sa'd- ;justed, is Iplaced opposite `a Vslit 'in the l"cathode 'surface *In-certain cases, it is advantageous to exert 'a C; fdiierential 'action on :the electrons, "according .to

Whether they have incompletely'participatedor -have not participated :at all -in the interaction. These electrons travel, in general, -at Ldiierent speeds' and 'their trajectories fare `4oi differentl'di- 7o -fameters In order .to exert such differentialv ac- -tion,use may be made of the `productionof an 'additional iield `'that has a particular distribution in the anode-cathode space and, in particular, widens towards the cathode. Figs. 8 to v11 show 75 several embodiments of suchV a -`iield.

sesame tional eldof conical shape that opens towards the cathode and enables additional speeds to be imparted to the electrons, said speeds being different according tothe radial distanceibetween their trajectory 'andthe cathode. Y.

i InFig'. 9, the'same' result is obtained by introducing an additional electrodeBa into the -cath-'- ode slit and adjusting its voltage.

According to Fig. 10, an embodiment has been shown that makes use of the two arrangements of Figs. 8 and 9 simultaneously.

According to Fig. 11. the desired eld is formed by a combination of electrodes that corresponds to a duplication of the arrangement of Fig. 10, in order to obtain a more gradual adjustment. In most cases, in order not to complicate the design of the tube, it is preferable to use only a single curved electrode.

By thus returning the unused electrons into a state of interaction with the field, the invention enables the emitting surace of the cathode to be decreased for a tube of a given power.

Instead of acting on the electric field, it is possible to produce all the effects described by deforming the magnetic eld, between the input and output terminals of the tube, i. e. in the portion of the tube that does not participate in the energy exchange. According to the above mentioned formula,

an increase in the magnetic field B changes the speed of the electrons in the same direction as a decrease in the electric field E. This adustment of the magnetic field applies more particularly to the case in which the diameter of the negative electrode B is large. This may be obtained, either by providing additional coils, or by giving a predetermined shape to the pole pieces. In practice, this method of adjustment involves constructional diiculties and is not desirable. It should only be contemplated in combination with the adjustment of the electric field.

In order to avoid self-oscillation, it is necessary in any case to prevent a portion of the high-frequency energy obtained from the output terminal S from continuing the cycle inside the tube and reaching the input terminal E. This can be obtained by placing and constructing said terminals in such a manner as to avoid any coupling between them, and by giving the anode wall, which is located between these two terminals and which does not conduct heavy currents, a high natural resistance.

What I claim is:

1. In an electron ampliiier for electromagnetic waves comprising an emissive cathode, means :tor establishing a substantially time-constant magnetic field, and electron beam developing means, said beam being located within said field, the lines of force of the field, in a given direction, being substantially parallel to the surface of the said cathode; the combination which comprises two substantially parallel conductors having their surfacesparallel to the lines of force of the magnetic iield, the conductors being curved along the arc of a circle concentrically to each other to define an interaction duct, the cathode being located between the two conductors adjacent one of the ends thereof, terminal connections to the conductors and a source of potential connected thereto thereby to produce between said 'conductors a difference of potential giving rise to a substantially time-constant electrostatic field substantially perpendicular to the said time-constant magnetic field, at least one of the conductors being divided into a first operative Yportion including *elements forming anelectrical delay line' wherein interaction between said electron beam and said waves occurs and into a second inop- 1o line is less than in space and substantially equal to the velocity of electrons in the duct, said electron velocity being determined by the ratio of the intensities of the electrostatic and magnetic fields, the said delay line having radio frequency input and output extremities separate from each other to enable mutual decoupling thereof and to prevent feedback oscillations, the said extremities being provided with means for coupling to outside circuits for exciting an electromagnetic wave in the radio-frequency input terminal and for collecting amplified energy at the radio-frequency output terminal, the said operative and inoperative portions of the delay line being complementary to each other to form a complete circle, means being provided in said inoperative portion adjacent to the output extremity of the delay line for collecting the electrons having passed through the portion of the duct co-extensive with said operative portion and which are traveling close to the conductor raised to the higher potential, said last named means extending into the regi-on filled by said electron beam and incompletely obstructing the cross-section of said beam.

2. An amplifier in accordance with claim 1 wherein said last named means comprises a conductive member intermediate the two conductors and extending parallel therewith and a' baffle eX- tending from said member to the electrode of higher potential, said member dividing the'duct into two channels, the channel close to the said electrode of higher potential being transversely closed by the said baie.

3. An amplifier in accordance with claim l including a collecting electrode located between said radio-frequency input and output extremities comprising a metallic screen inserted in the circular duct between said terminals, and a terminal connection for imparting to said electrode a potential different relatively to the cathode from that of the conductor raised to the higher potential.

4. An amplifier in accordance with claim 1 wherein the portion of one of the conductors coeXtensive with said inoperative portion of said other conductor is divided into at least two segments insulated from each other and from the rest of the conductor, each said segment being supplied with a variable potential.

5. An amplier in accordance with claim 1 further comprising means for varying the said timeconstant electrostatic field in said inoperative portion said means comprising auxiliary electrodes close to said inoperative portion with means for impressing variable potentials thereupon.

6. An amplifier in accordance with claim 5 further comprising means for varying the intensity 2,633,5054 7;? of the-saiditimefconstantfmagnetiofield across; REFERENCES CITED.. said,-noperativeeportionsaid means consisting of aspredetermned-formof magnetioeldproducn lef this patent; v

The followingj refereruxes are-of record :in wthef means.-

7; An amplifier-in accordance with claiml 5 UNITED 'STATES'PATENTS wherein the' inoperative portion of said conduc Number'V Name Date tor complementaryto said delay line is formed of Y 2,289,756 Clavieret al. JulyV 14, 1942 afmaterialofhigh resistivity. 2,300,052 Lindenblad v Oct. 27, 1942;

2,511,407 Kleen etal. June 13; .17950 LERBS. 10 2,531,9721 Doehler et al Nov. 2 8, 1950 

